Conventionally, to control the movement of dampers in air ducts, pneumatic, electronic and electrical actuators are used. There are a number of disadvantages of using a pneumatic controller which include, for example, the drifting of the calibration point of the pneumatic controller over time, and the susceptibility of pneumatic lines to contamination from moisture due to condensation or lubricating oil from the compressor. Even though the current crop of HVAC electronic controllers are now microprocessor based, no reliable electronic actuators have yet been found. Moreover, with microprocessor based controllers, the old problems associated with pneumatic controllers have been replaced by a new set of problems which include the problem of converting different types of signals, as for example converting the digital signals output from the microprocessor to analog signals and further to pneumatic signals. There is therefore the added cost of the equipment for making those signal conversions. As for the electrical type of actuators that use motors and gears to drive the damper, experience has shown that the complexity of such actuators tends to make them unreliable and expensive.